Hey,

The details which are necessary to be filled are marked with red asteriss  in the registration form. Logon to your portal from where you have to fill the registration form and see whether they are asking for the CPT details and whether bit has been marked red.

If not marked red then it's not a necessity to fill it. If marked red then you have to fill it. You can search your e-mail I'd for the login or roll number related information that you have provided at the time if registration for CPT

Hope that helps.

Thank you